<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="box">hello</div>
    <script>
        const box = document.getElementById('box');

        const elB = document.createElement('b');
        elB.innerHTML = 'hello btag'

        box.append(elB)
        // console.log(box, elB);

    </script>
</body>

</html>